Okay, I think I know where the problem is.
First redownload the zip and reimport it selecting overwrite style.
If that doesn't fix it, check this
admincp -> Styles & Templates -> Citrus Splatter -> All Style Options
and scroll down to
Table Header (Customized in this Style)
Make sure the background is
Code:
#5C7099 url(CitrusSplatter/gradients/gradient_thead.gif) repeat-x top left
and the font color is